The University of Maryland, Department of Chemistry and Biochemistry, College Park, MD, United States.
The University of Maryland, Department of Cell Biology and Molecular Genetics, College Park, MD, United States.
J Mol Biol. 2021 Jul 23;433(15):167100. doi: 10.1016/j.jmb.2021.167100. Epub 2021 Jun 11.
Bacterial NusG associates with RNA polymerase (RNAP) through its N-terminal domain, while the C-terminal domain (CTD) forms dynamic interactions with Rho, S10, NusB and NusA to affect transcription elongation. While virtually all bacteria encode for a core NusG, many also synthesize paralogs that transiently bind RNAP to alter expression of targeted genes. Yet, despite the importance of the genes they regulate, most of the subfamilies of NusG paralogs (e.g., UpxY, TaA, ActX and LoaP) have not been investigated in depth. Herein, we discover that LoaP requires a small RNA hairpin located within the 5' leader region of its targeted operons. LoaP binds the RNA element with nanomolar affinity and high specificity, in contrast to other NusG proteins, which have not been shown to exhibit RNA-binding activity. These data reveal a sequence feature that can be used to identify LoaP-regulated operons. This discovery also expands the repertoire of macromolecular interactions exhibited by the NusG CTD during transcription elongation to include an RNA ligand.
细菌 NusG 通过其 N 端结构域与 RNA 聚合酶 (RNAP) 结合，而 C 端结构域 (CTD) 则与 Rho、S10、NusB 和 NusA 形成动态相互作用，从而影响转录延伸。尽管几乎所有细菌都编码核心 NusG，但许多细菌还合成了暂时与 RNAP 结合的同工酶，以改变靶向基因的表达。然而，尽管它们调节的基因很重要，但大多数 NusG 同工酶的亚家族（例如，UpxY、TaA、ActX 和 LoaP）尚未得到深入研究。本文中，我们发现 LoaP 需要位于其靶向操纵子 5' 启动子区域内的小 RNA 发夹结构。LoaP 以纳摩尔亲和力和高度特异性结合 RNA 元件，与其他 NusG 蛋白不同，后者尚未显示出 RNA 结合活性。这些数据揭示了一种可用于识别 LoaP 调节操纵子的序列特征。这一发现还扩展了 NusG CTD 在转录延伸过程中表现出的大分子相互作用的范围，包括 RNA 配体。
